The prevention or therapeutic reversal of preneoplasias in humans has been little studied. Cervical intraepithelial neoplasia (cervical dysplasia) represents an excellent model to study preneoplasia inasmuch as the lesions can be safely and easily monitored in response to an intervention and therapeutic agents can be delivered locally, thereby obviating systemic side-effects. We have developed a simple delivery device consisting of a cervical cap and collagen sponge which allows constant exposure of the therapeutic agent to the cervix. We have conducted phase I toxicity and phase II efficacy trials using the retinoid beta-all-trans retinoic acid. The results were sufficiently encouraging that we have planned a stratified, randomized trial (cancer control phase III) of beta-all-trans retinoic acid versus placebo cream in a total of 300 patients with moderate and severe dysplasia. This application seeks support for continuation of this trial.